1. Field of the Invention
The present invention is related to a packet communication apparatus.
2. Description of the Related Art
In public communication networks and bank communication networks, since high reliability is required, various operation and maintenance requirements are satisfied. For instance, conditions of communication paths must be monitored, fault states must be immediately detected, and fault location must be avoided. The presently available public transmission networks have conducted the SDH (Synchronous Digital Hierarchy, or, known as “SONET” in the North America) system. This SDH system is normally defined by ITU-T recommendation G.707 (see International Telecommunication Union Telecommunication Standardization Sector). The SDH system may provide these OAM (Operation And Maintenance) functions (in particular, refer to 9.2.2 SOH bytes description of Recommendation G.707). In this SDH system, a header called a section overhead is applied to a frame on which user signals called VC (Virtual Container) are multiplexed, and then this frame is transmitted between the SDH systems. To this section overhead, the embedded type OAM functions are defined, for example, the BIP (Bit Interleave Parity) function capable of monitoring the error rate of the transmission path; the AIS/RDI notifying function capable of mapping the protocols used to switch the transmission path between the stations and also capable of notifying the malfunction of the transmission path and the fault in the transmission path; and the function capable of establishing the confirmation communication between the stations. The information acquired by the embedded type OAM function may be used to trigger the avoiding operation of the fault location, may be sent to the network management system capable of surveying the condition of the network so as to be used for executing the operation/maintenance of the network, and also may be used as the reply data to the claims made by the customers. Since the transmission network having the high reliability and the high maintenance characteristic is established by employing such an embedded type OAM function, this transmission network can satisfy the high reliability requirements of the public communication network and the bank communication network.